we will go through activity 16.8 class 8 science chapter 16 Light in which we will discuss how the iris controls the amount of light entering the eye through the pupil. You should also go through activity 16.5 to get more about reflection.
Activity
· Look
into your friend’s eye.
· Observe the size of the pupil.
· Throw
light on her eye with a torch.
· Observe
the pupil now.
· Switch off the torch, and observe her pupil
once again.
· Do you notice any change in the size of the
pupil?
· In which case was the pupil larger?
· Why do you think it was so?
· In
which case do you need to allow light in the eye when the light is dim or
bright?
 |
| Activity 16.8 Class 8 Science Chapter 16 Solution |
Observation and explanation
The pupil is an aperture in the centre of the iris. The
involuntary muscles adjust the size of the pupil and so control the amount of
light entering the eye through the pupil.
When light is thrown on the eye, the size of the pupil becomes
smaller and a lesser amount of light is allowed to enter inside the eye.
In dim light, the pupil becomes wide to allow light to enter
the eye.
So, the iris controls the amount of light entering the
eye by contracting and dilating to a range
of the size of the pupil.
Conclusion
This activity shows how the iris controls the amount of
light entering the eye through the pupil.
Related Topics
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